Strokes In Patients With Narrowed Carotid Arteries May
Be Due To Other Causes

CHICAGO, IL -- March 14, 2000 -- Strokes occurring in patients with severe
narrowing of the carotid artery are commonly due to other causes, according to
an article in the March 15 issue of The Journal of the American Medical
Association (JAMA).

Henry J.M. Barnett, M.D., from the John P. Robarts Research Institute in
London, Ontario, and colleagues analyzed data from 2,885 patients with
symptomatic internal carotid artery stenosis (narrowing of one of the main
arteries that supplies blood to the brain). The patients participated in the
North American Symptomatic Carotid Endarterectomy Trial (NASCET), in which they
were randomly assigned to receive either an endarterectomy (an operation that
removes material [such as atherosclerotic deposits] and part of the lining of an
artery to relieve blockages and increase blood flow) or medical management for
the treatment of carotid artery stenosis.

The researchers followed the patients for an average of 5 years and
categorized subsequent strokes by three possible causes: large-artery (carotid)
blockage, cerebral lacunar (small areas of damage to the brain caused by
blockages in smaller branches of arteries that supply blood to the brain), or
cardioembolic (blockage caused by a clot traveling from the heart). During the
follow-up period, 749 patients had 1,039 strokes. The overall risk of first
stroke after entry into the study was calculated as 2.6 percent for
cardioembolic, 6.9 percent for lacunar, and 19.7 percent for large-artery.

The researchers found that for those patients with symptoms with less than 70
percent stenosis, approximately 35 percent of the strokes were unrelated to
narrowing of the carotid artery. For those patients without symptoms and with 60
to 99 percent stenosis, approximately 50 percent of the strokes were unrelated
to narrowing of the carotid artery. "The cause of subsequent strokes in
similar types of patients should be considered when making treatment decisions
particular involving carotid endarterectomy for patients with asymptomatic
carotid stenosis, since lacunar and cardioembolic strokes cannot be prevented by
endarterectomy."

"The results of this study demonstrate that even in the presence of
large-artery lesions, strokes arise from a variety of causes," the
researchers write. "Expectations of benefit from endarterectomy in
symptomatic patients with moderate disease or in asymptomatic subjects must
consider the evidence that a large number of future strokes will not be related
to the carotid artery lesion," the authors note.

"The risk of stroke expected from the large-artery lesion is only part
of the story. In patients with carotid stenosis suspected of causing ischemic
events, risk factors must be modified," the researchers write. "Before
deciding on the final treatment strategy, consideration should be given to
investigations to identify other potential causes of stroke." (JAMA.
2000;283:1429-1436)